The semiconductor integrated circuit (IC) industry has experienced rapid growth. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. However, such scaling down has also been accompanied by increased complexity in design and manufacturing of devices incorporating these ICs, and, for these advances to be realized, similar developments in device fabrication are needed.
As merely one example, many fabrication steps involve the formation and manipulation of thin films of material formed on a substrate or wafer. Defects, imperfections, irregularities, and contaminants in these film layers may undermine the fabrication process and may precipitously affect both yield and device performance. Many of these types of defects compound as the films are layered upon each other during the fabrication process. Thus, the importance of uniformity and precise application cannot be overemphasized.
Spin coating is one technique for forming a thin layer of material on a substrate that has proved satisfactory in some applications. Spin coating may involve depositing a material in liquid form at the center of a substrate and spinning the substrate to drive the liquid to the edges. In this way, spin coating leverages the centrifugal tendencies of the liquid to produce a film of significantly uniform thickness.
However, while existing spin coating techniques have been generally adequate, the potential for future improvements still exists. For example, uniformity of the final film may still be improved. As another example, because many advanced fabrication processes rely on increasingly expensive materials, improved coverage using less liquid may meaningfully reduce cost per unit. For these reasons and others, additional improvements to spin coating techniques hold the potential to improve fabrication yield and to reduce cost and waste.